WATER-GLANDS IN THE LEAF OF SAXIFRAGA CRUSTATA, 407 
The DevELopMENT of the WatER-GLANDS 7” the Lear of 
SAXIFRAGA cRUSTATA. By WaLTER GarpIner, Natural 
Science Scholar of Clare College, Cambridge. With 
Plate XXIII. (From the Botanical Laboratory, Cam- 
bridge. 
THE leaves of Sazifraga crustata—oblong obovate, with 
a crenate margin—are arranged in a rosette on the axis, the 
internodes of which are hardly at all developed. 
In the centre of each of the little crenate lobes with which 
the leaf is fringed is seen a pit or depression, covered with a 
white incrustation, which appears to spread from the pit, 
covering the entire lobe, and even extending over other 
parts of the leaf as well. The incrustation consists, appa- 
rently, of calcic carbonate. 
If a transparent preparation be made of the leaf (fig. 1) it 
is seen that the peripheral terminations of the fibro-vascular 
bundles which ramify through the mesophyll present the 
appearance of anumber of dilatations. Each such dilatation 
is placed immediately under the bottom of the depression of 
each lobe, and constitutes what is known as the water- 
gland. 
The mature glands of this plant were first described by 
Unger,! but, so far as I am aware, their development has 
not been investigated, and it is the object of the following 
paper to deal with this latter question. Since the develop- 
ment of the leaf and its tissues are necessarily very closely 
connected with that of the glands, it seems best to consider 
first the development of the leaf as a whole, and then that 
of the glands. 
Development of the leaf.—The punctum vegetations of 
Sazifraga crustata is a hemispherical mass of meristematic 
cells, the external layer of which is differentiated as a 
dermatogen (fig. 2). The first rudiment of the leaf appears 
as a lateral outgrowth of this primary meristem, covered, of 
course, by dermatogen. At first the rudimentary leaf en- 
larges by rapid apical growth, and thus the first or terminal 
lobe is formed; with its formation apical growth ceases. 
The further elongation of the leaf takes place by tne activity 
of a zone of meristematic cells at its base. Hence, its sub- 
sequent growth is basipetal, ¢.e. the youngest lobes are 
nearest the base. But although the growth of the leaf, as a 
1 Beit. 3, ‘Physiol. d. Pfilzn. viii. For the literature of the subject, 
see De Bary. ‘ Vergl. Anatomie,’ pp. 113, 389. 
